#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<assert.h>

void* my_memcpy(void* des, void const * src, size_t num) {
	assert(des && src);
	void* ret = des;
	while (num--) {
		*(char*)des = *(char*)src;
		des = (char*)des + 1;
		src = (char*)src + 1;
	}
	return ret;
}
int main() {
	char arr1[] = "abcdefg";
	char arr2[] = "efu";
	printf("%s\n", arr1);
	my_memcpy(arr1+4, arr2, 3);
	printf("%s\n", arr1);
}